Mechanism for sharpening the bell knife of a skiving machine



E. H. BECK Nov. 17, 1964 MECHANISM FOR SHARPENING THE BELL KNIFE OF A SKIVING MACHINE 2 Sheets-Sheet 1 Filed May 18, 1962 lllllllll l lllllllllllm||||||| n|| ||||u|m HIHIIHHHIIIIH E. H. BECK 3,157,008

MECHANISM FOR SHARPENING THE BELL KNIFE OF A SKIVING MACHINE Nov. 17, 1964 2 Sheets-Sheet 2 Filed May 18, 1962 m Q So K w m Q x m M UW w w Q W N M United States Patent 3,157,008 l /[ECHANISM FOR SHARPENING THE BELL KNIFE GE A SKIVING MACHINE Edwin H. Beck, Lemay, M0., assignor to Manufacturers Supplies Company, St. Louis, Mo., a corporation of Missouri Filed May 18, 1962, Ser. No. 195,790 6 Claims. (Cl. 51-247) This invention relates to mechanism for maintaining the cutting edge on a rotary knife of a skiving machine, and more particularly to a mechanism for this purpose which Will maintain uniformity of the cutting edge during the useful life of a knife of this kind.

Vast experience has been obtained by manufacturers of this type of skiving machine pertaining to the degree of bevel suitable for the edge on a rotary type of knife with respect to its particular intended purpose for which the particular machine is to function taking into account all of the conditions of the use. Best results depend upon maintaining a similarity of bevel, at least near the cutting edge, while at periodic intervals a keen even edge is ground on the knife. Customer satisfaction is dependent upon machine function and a change in bevel, or a dull or Wavy edge on the knife, will not produce a satisfactory skiving action. In fact, the output of the machine is so affected that a large percentage of waste results.

For many years, skiving machines have been provided with grinding wheels to resharpen the knife periodically as the machines are used. It will be readily appreciated that if the wheels are set originally to cut the proper bevel on the knife, this setting will be temporary only because of the material removed from the Wheel and from the knife causes a relative change in position. To avoid one aspect of this change, and for other reasons having to do with other functions of the machine, knives were provided with adjustable mountings whereby they could be adjusted so that the cutting edge would be restored to its original position with respect to other parts of the machine as well as the grinding wheel. In addition, the grinding wheels were provided with movable mountings so as to set their peripheral face with respect to the beveled edge of the knife. These changes in the machine overlooked one factor having a marked effect on maintaining the effectiveness of the grinding wheel. As will be readily appreciated, the peripheral surface of the wheel has, if true, a near line contact axially of the conical surface formed by the beveled edge on the knife. Any substantial departure from this relation between Wheel and knife, such as a concavity in the peripheral surface of the wheel due to wear, which results in contact between the wheel and the knife near one edge, or the other, of the wheel; any eccentricity from wear on the wheel, etc.; have an influence upon the keenness of the knife edge, and the trueness of the cutting edge of the knife. This is inherently so because both wheel and knife are rotating during the grinding operation and on axes which are at right angles.

Once these causes were correctly diagnosed, then it became customary to make periodic service checks by sending trained personnel to a shoe factory, who were capable of correcting these ditficulties. This, of course, required costly shutdowns of the machines for one thing, and, for another, since hand tools, such as wheel dressers, were used, it frequently occurred that more than one application of a hand dressing tool would be necessary before the grinding wheel was true. This resulted in shortening the expected life of the wheel unnecessarily.

The next step in skiving machine improvement amounted to no more than building such a hand operated dressing tool into the skiving machine so that the machine operator could periodically attempt to true the Wheel.

Patented Nov. 17, l9fi4 None of these mechanisms, however, amounted to an improvement since none took into account the fact that the wheel changed diameter and that the dressing tool became worn. Consequently, the problem was not solved but merely aggravated. Whereas, the built-in hand dressing tool was originally thought to be a meritorious sales feature, quite the opposite happened after a few machines Were put under the control of unskilled persons.

It is one of the objects of this invention to provide a mechanism for sharpening the rotary knife of a skiving machine which is consistent in maintaining similarity in the angle of bevel on the knife at least near the cutting edge, a true cutting edge on the knife, and one which is so simple and foolproof as to be satisfactory in the hands of unskilled persons, at least, after simple instructions as to procedure.

It is another object of this invention to provide an improved wheel truing mechanism for this use.

It is still another object of this invention to provide an improved wheel truing mechanism for use as part of a mechanism for restoring, or maintaining, the true cutting edge on a rotary knife for a skiving machine.

According to this invention, a power driven rotatable grinding wheel is movably mounted to swing to and from the beveled edge of a rotary knife in a skiving machine in such a manner that a diameter across the wheel is perpendicular to the conical surface formed by the bevel on the sharpened edge of the knife when the knife is adjusted to proper operating position. A wheel truing tool is mounted to move in a path parallel to the axis of rotation of the rotary knife. This path of movement would also -be perpendicular to a second diameter of the wheel which is in turn at right angles to the axis of rotation of the rotary knife. 0n the tool is a truing edge, or edges, which engage the wheel peripheral surface at a point which coincides with a wheel diameter having the same angular relationship with respect to a diameter through the wheel perpendicular to the axis of rotation of the knife as the angular relationship of the aforementioned diameter which is described as perpendicular to the conical surface formed by the bevel on the sharpened edge of the knife. Expressed another way, with respect to a diameter through the wheel which is perpendicular to the axis of rotation of the rotary knife, the truing edge of the truing tool meets the periphery of the wheel at a point on one side of said diameter displaced the same amount as the mean point of contact between the wheel and the bevel on the other side of this diameter. With such a relationship, it will be inherent that the trued peripheral Surface on the Wheel is perpendicular to the axis of the rotating knife, and, so long as this condition prevails, the knife and wheel can otherwise be set so that the angle of bevel near the cutting edge of the knife will remain unchanged during sharpening even if the trued peripheral surface on the wheel is not parallel to the grinding wheel axis. It is likewise inherent that, when the knife is adjusted to compensate for wear, the relative angular relationship defined between wheel and knife edge will remain substantially constant regardless of wheel size. The fact that these conditions are inherent in the mechanism results in a wheel truingaction which forms a peripheral surface on the wheel to cut an angle of bevel similar to the original angle on the knife, at least near the cutting edge, and in a uniform manner giving a keen knife edge which is true and not wavy. Thus, the cutting edge and the angle of bevel adjacent the edge is maintained even though more remote parts of the bevel edge may vary in 3 unskilled persons with uniformly satisfactory results when simple instructions are followed.

Other objects and advantages of the instant invention will become apparent to those skilled in the art from the following detailed description which is in such full, clear and exact terms as to enable any person skilled in the art to make and use the same when taken with the accompanying drawings, forming a part thereof, and in which:

FIG. 1 is a top plan view schematically illustrating the relationship between the parts in a sharpeningmechanism for a bell knife of a skiving machine;

FIG. 2 is a front elevational viewof a portionof a standard type of skiving machine with parts broken away and in section;

FIG. 3 is a front elevational view of a portion of a skiving machine shown in FIG. 2 illustrating the internal construction as it would appear with. the end cover of the housing swung to open position on its hinges;

FIG. 4 is a sectional View of the line 44 of FIG. 2 looking in the direction of the arrows;

FIG. 5 is a front elevational view of the truing tool holder shown in FIG. 4; and

FIG. 6 is a rear elevational view of the truing tool holder shown in FIG. 4.

With reference to FIG. 1, therein shown schematically is a bell. shaped knife K for a skiving machine which has a beveled edge B forming the cutting edge C on the open. end of the bell shaped knife K. It will be understood that the bell shaped. knife K is mounted to rotate on an axis, indicated by the line CD, fixed by bearings which are a part of the base of the machine. Oneexample of the specific bearings for mounting the knife K will be Also mounted onthe base of thethe exact relationship between grinding wheel and bevel B, hereinafter described. Bearings on the-end of the 7 swinging arm S rotatably mount the grinding wheel 'G.

which is driven by a belt and pulley mechanism, hereinto the axis of rotation CD of the knife K. The mounting M is also capable of limited rotational movement about the axis AB, whichmovernent is restricted in this direction by a mechanism which will be hereinafter described and.

is generally illustrated here as comprising. the parts L. A truing edge, such as a diamond D, is mounted in a setting S held in a socket of the truing tool holder TH in such a manner that it contacts the peripheral surface of the grinding wheel G along the diameter thereof EF-, whe n the grinding wheel periphery is slightly; spaced from the bevel B, and the grinding Wheel G is arranged on its arm S so that when in contact with the bevel B the, wheel diameter JH will be perpendicular to, the conical surface formed on the edge of the knife by the bevel B. The,

diameters EF and J H bear the same angular relationship with respect to the diameter PP which is perpendicular to both the lines AB-and CD. Stated. another way, the perpendicular PP bisects the angle betweenthe diameters EF and J H.

When this relationship is established between the parts,

it will be maintained regardless of. the size of the grinding wheel G. For example, suppose the grinding wheel is worn down until it has a diameter indicatedas G. When this occurs, the mounting M permits the truing tool holder TH to move alongthe axis AB until the edge D is in contact with the periphery of the wheel when in the same relative position as wheel G. The edge D then lays on the diameter EF through the center of the wheel G and the relationship between the diameters BF and JH remains constant with respect to a diameter through the wheel G.

As each subsequent truing operation of the truing tool reduces the diameter of the Wheel G, a peripheral surface of the wheel G will be dressed to an angular relationship, such as to bear a constant relation with the bevel B regardless of the wheel size. In other words, the peripheral surface of the wheels G and G will remain perpendicular to the axes AB and CD at the point of contact between the truing edge D. Since the edge D contacts the wheel, regardless of the wheel size, at a point having the same peripheral distance from the line PP as the point of initial contact between the wheel G and bevel B along the diameter 1H, the relationship between the parts remains constant..

The remaining views in the drawings, FIGS. 2 through 6, show a construction forming one example of how the above described principles are applied to a form of skiving machine. a

The skiving machine, shown in FIG. 2, has a housing 1 mounted on a table 2. The end of the housing 1 has a cover 3 which is hingedly mountedto move toward and away from the main housing 1 of the machine. The top surface of the housing 1 forms. a work surface 5 which is apertured at 6 to expose the upper surfaceof a work feeding roll 7. A bracket 9 has bearings. 10 which re tatably mount the feed roll 7 and the bracket 9 is suitably mountedso as to providefor adjustment of the peripheral surface of the feed roller 7 with respect to the knife 12. Shaft 13 secured to the closed end. of the rotary knife 12 isrotatably mounted in suitable bearings 14 and 15, one of which, 15, is a rotatable sleeve in the housing 1. There is a collar.17 on the shaft 13 and bearing against the. right face of the collar 17 is a sleeve 18;

24 on a shaft 25. Secured on the part 13 is a flangecollar 26; This collar 26 is surrounded by a coil compres sion spring- 27 constantly urging the. shaft 13 in a direction to engage the collar, or flange, 17 with the adjae cent face of-sleeve 18. by engagement with a suitable.

collar. on the shaft 13. or the hub of. pulley 30.. On the end of the shaft 13 is a pulley 30 engaged by a belt in order to drive the shaft 13 and in turn rotate the knife 12. The spring frictionally resists turning of part 15.

with housing 20. The construction, herein described so far, is that of a conventional skiving machine. Knife. 12 in such a machine can be positioned with respect to the feed roller 6 by the adjustment provided .in the threaded engagement between housing 20 and sleeve 18 during rotation of the shaft 25 mounting the worm gear 24. Shaft 25has a. manually adjustable. knob exposed outside the housing 1 by which housing 20 can be. rotated to move the edge of the bell knife 12 to theleft, or by rotation of the knob in the opposite direction to permit the spring 27 to move the edge of the bell knife 12 to the rig t.

It is also customary in skiving machines to provide a grinding wheel G for sharpening the edge of the knife 12. As shown in FIG. 2, the axis of rotation of the knife 12, whichis indicated by the line CD, bisects the peripher-. al surface of the grinding wheel G. A hearing housing 32 rotatably supports a shaft 33 to which the grinding wheel G is secured. A pulley 34 on the opposite end of the shaft 33 is driven by a belt 35 so as tocontinuously rotate the grinding wheel G. Arm S mounting the hous- 1ng 32 swings on an adjustable pivot 37 supported by cars 38 and 39 integral with the back wall of the housing 1. On the arm S is a pin engaged by a coil spring 49 which biases the arm S in a direction to engage the periphery of the grinding wheel G with the bevel edge B of the knife 12. The spring 40 has one end attached to a pin on the arm S and the other end secured to the front wall 1 of the housing. Also on the front wall of the housing is a knob 42 which is threaded in the front wall of the housing and has a free e nd bearing against the arm S so as to limit the swinging movement of the arm S in a direction to engage the grinding wheel G with the bevel B on the knife 12. It might be mentioned here that there is an arm 44 mounted on the housing 1 which in turn forms the support for a presser foot head. The parts so far described are standard construction in one type of well-known skiving machine, known in the trade as the model 10 and this construction will serve the purposes of illustrating how the invention can be applied to any machine of this general kind.

As heretofore stated, the end of the housing 3 hinges on the back wall of the housing 1 so as to swing from the position shown in FIG. 2 to the position shown in FIG. 3. As shown in this latter figure, the end of the housing 3 has a hinge ear 46 received between similar cars 47 and 48 on the housing 1. These ears are hingedly connected by a suitable pin. On the inside face of the hinged housing 3 is a protruding boss 59 apertured at 51 and at 52. This portion of the housing is better shown on an enlarged scale in FIG. 4. The boss 54 is hollow and is threaded at 54 to receive the threaded sleeve 55. Rotatable within the sleeve 55 is a shaft 57 which protrudes through the aperture 51. Shaft 57 has a fixed shoulder 58 which bears against one end of the sleeve 55. The opposite end of the shaft 57 is threaded to receive knob 60 and lock nut 59. The aperture 52 receives a fixed rod 62 which projects from the boss 56 in the same direction as, and parallel to, the end of the shaft 57. The adjacent end of the shaft is stepped at 65 to form a shoulder 66. The stepped end of the shaft 65 is received within sleeve 63 of the truing head TH and is held in abutment with the shoulder 66 by the set screw 69 threaded through the wall of sleeve 68. Integral with the sleeve 68 is a second sleeve 7t? which forms an adjustable holder for the setting SE in which the truing edge, in this case diamond D, is mounted. When the sleeve 68 is fixed on the end of the shaft 57 in this manner, rotation of the knob 6% in turn can rock the sleeve 68 and the truing edge, diamond D. The amount of rock permitted by the knob 60 is limited by a construction of the tool holder TH. For this purpose, the tool holder has a pair of parallel extending members, or flanges, 75 and 76 as shown in FIGS. and 6. These flanges are apertured at opposite points at one end and threaded to receive therein a pair of set screws 78 and 79. Each of the set screws in turn may carry a lock nut 80 and 81, respectively. The set screws 78 and 79 are aligned with the fixed rod 62 so that the amount of rotation of the shaft 57 by the knob 6t can be adjustably fixed. Thus, the arc of swinging of the truing edge, or diamond D, is also adjustable by means of these same set screws. Preferably, this are of swing which is permitted for the tool holder TH is such that the diamond D will move from edge to edge of the grinding wheel G, but never off the surface of the grinding wheel G. The construction, just described, of the truing mechanism occupies a position with respect to the grinding wheel and the knife, as heretofore explained with respect to FIG. 1.

In the machine above described, the feed roll 7 may have a surface which is closest to the knife edge 12 covered with emery. When such a feed roll is used, the feed roll should be adjusted so that it barely touches the edge of the knife. If properly adjusted in this respect it will remove the burr which may be formed on the cutting edge of the knife. Although the feed roll, in the above instance, constantly engages the inner surface of the bell knife, the outer surface of the knife 12 at the bevel B rotates clear of the grinding wheel G. In other words, knob 42, is turned to thread inwardly against the arm S so that the grinding wheel periphery just clears the surface of the bevel B of the knife 12. However, the arrang ment of parts is such that adjustment of the knob 42 moves the wheel away from the truing edge D so that no 6% damage can occur to the wheel if the knob 42 is carelessly adjusted.

Sharpening of the knife edge is accomplished by rotating the knob 42 sufficient to allow the spring 40 to bring the peripheral surface of the grinding wheel G in contact with the bevel B on the knife 12. The engagement should be light under most conditions and the spring 40 is chosen for this purpose. In order to maintain the angle of the bevel B, it will be necessary from time to time to true the peripheral face of the grinding wheel G. This procedure is accomplished by rotating the knurled surface 61 of the sleeve 55 until the edge, or diamond D, engages the peripheral surface of the wheel 6. This can be readily determined by sense of feel. The operator then grips the knob 60 and rocks the truing holder by twisting the knob 60 in alternate directions as fixed by the limit stops which are set screws 78 and 79. Preferably, the truing procedure is performed with the grinding wheel in a position to just clear the bevel surface B, and after the truing step is carried out, the tool is retracted by rotation of the knurled knob 61 while the sharpening procedure is performed by rotation of the knob 42 in a direction to allow the wheel G to be pressed against the beveled surface B.

Changes in and modifications of the construction described may be made without departing from the spirit of my invention or sacrificing its advantages.

Having thus described the invention, what is claimed and desired to be secured by Letters Patent is:

1. A mechanism for sharpening the bevelled cutting edge of a driven rotary bell shaped knife in a skiving machine comprising,

(1) a driven rotary grinding wheel mounted to move substantially in a plane containing the axis of rotation of said rotary bell shaped knife and having its axis of rotation substantially at right angles to the axis of rotation of said rotary bell shaped knife, said grinding wheel being arranged with a diameter thereof substantially perpendicular to a. substantially conical surface formed by said bevelled cutting edge,

(2) a truing tool including a truing edge engaging the peripheral surface of said grinding wheel at a point on a grinding wheel diameter different from the diameter substantially perpendicular to the bevelled edge which forms substantially the same angle with respect to the axis of rotation of said knife as does the diameter thereof substantially perpendicular to the substantially conical surface formed by said bevelled cutting edge.

2. In a skiving machine of the type using a rotary bell shaped knife with a bevelled cutting edge and means for sharpening said cutting edge including a. driven rotary grinding wheel mounted to move substantially in a plane containing the axis of rotation of said rotary bell shaped knife with the axis of rotation of said grinding wheel substantially at right angles to the axis of rotation of said rotary bell shaped knife, said grinding wheel when moved to and against that knife having a relation therewith in which a diameter thereof is substantially perpendicular to a substantially conical surface formed by said bevelled cutting edge, the improvement in said means comprising,

(1) a wheel dressing tool including a truing edge for engaging the peripheral surface of said grinding wheel,

(2) and means mounting said wheel dressing tool for movement parallel to the axis of rotation of said bell shaped knife and for movement across the peripheral surface of said grinding wheel at points substantially in a plane through the center of the wheel which plane forms substantially the same angle with respect to the axis of rotation of said knife as does said diameter thereof substantially perpendicular to the substantial- 1y conical surface formed by said bevelled cutting edge.

3. The combination as defined in claim 2 in which the wheel dressing tool is a diamond held in a mounting to engage the peripheral surface of said grinding wheel.

4- The combinationsas defined in claim 2 wherein the means mounting said wheel dressing tool for movement parallel tothe axis of rotation of said bell shaped knife includes a shaft parallel with said axis and interengaging relatively rotatable threaded parts, one of which is fixed to a part of said machine and the other of which rotatably supportssaid shaft for rotary motion with respect to said part of said machine.

5. In a skiving machine of the type having a rotary bell shaped knife with a bevelled cutting edge and a mechanism for maintaining a sharp edge on said knife including a driven rotary grindingwheel mounted to move substantially in a plane containing the axis of rotation of said rotary bell shaped knife and having its axis of rotation substantially at right angles to the axis of rotation of said rotary bell shaped knife, which grinding wheel is arrangedto contact said knife by movement in said plane to a relationship in which a diameter thereof is substantially perpendicular to and in contact with a substantially conical surface formed by said bevelled cutting edge, the improvement in said mechanism comprising,

(1) a wheel dressing tool including a truing edge arranged to engage the peripheral surface of said grinding wheel,

(2) a shaft parallel with the axis of said rotary bell shaped knife and mounting said wheel dressing tool at one end thereof,

(3) relatively rotatable parts having interengaging' threads forming a support for said shaft, one of said parts being fixed to, apart of said machine and the other of said parts rotatably supporting said shaft for rotary motion with respect to said part of said machine, i l

(4) and means on said shaft to rock said shaft and wheel dressing tool, and means on said rotatable theaded part to adjust the wheelidressing tool with respect to said grinding wheel.

6. The combination as defined in claim 5 including means for limiting the rocking motion of said dressing tool to maintain said tool opposite the periphery of said grinding wheel.

References Cited by the Examiner UNITED STATES PATENTS 1,143,337 6/15 Walling 11.7 1,832,424 11/31 Rau 83-l74 XR 1,871,504 8/32 Einstein et al 12511 2,468,039 4/49 Cochrane et al 12511.7 2,726,412 12/55 Ruhr et a1 83l74 XR 2,755,600 7/56 Smith 125-41 XR FOREIGN PATENTS 543,645 6/56 Belgium.

J. SPENCER OVERHOLSER, Primary Examiner.

LESTER NI. SWINGLE, FRANK H. BRONAUGH,

V Examiners, 

1. A MECHANISM FOR SHARPENING THE BEVELLED CUTTING EDGE OF A DRIVEN ROTARY BELL SHAPED KNIFE IN A SKIVING MACHINE COMPRISING, (1) A DRIVEN ROTARY GRINDING WHEEL MOUNTED TO MOVE SUBSTANTIALLY IN A PLANE CONTAINING THE AXIS OF ROTATION OF SAID ROTARY BELL SHAPED KNIFE AND HAVING ITS AXIS OF ROTATION SUBSTANTIALLY AT RIGHT ANGLES TO THE AXIS OF ROTATION OF SAID ROTARY BELL SHAPED KNIFE, SAID GRINDING WHEEL BEING ARRANGED WITH A DIAMETER THEREOF SUBSTANTIALLY PERPENDICULAR TO A SUBSTANTIALLY CONICAL SURFACE FORMED BY SAID BEVELLED CUTTING EDGE, (2) A TRUING TOOL INCLUDING A TRUING EDGE ENGAGING THE PERIPHERAL SURFACE OF SAID GRINDING WHEEL AT A POINT ON A GRINDING WHEEL DIAMETER DIFFERENT FROM THE DIAMETER SUBSTANTIALLY PERPENDICULAR TO THE BEVELLED EDGE WHICH FORMS SUBSTANTIALLY THE SAME ANGLE WITH RESPECT TO THE AXIS OF ROTATION OF SAID KNIFE AS DOES THE DIAMETER THEREOF SUBSTANTIALLY PERPENDICULAR TO THE SUBSTANTIALLY CONICAL SURFACE FORMED BY SAID BEVELLED CUTTING EDGE. 